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Interdisciplinary approach to the mandibular therapeutic position in oral rehabilitation 115

Abstract The following article attempts to summarize the important elements that were highlighted during the last congress of the International Academy of Advanced Interdisciplinary Dentistry. The meeting objectives were to propose answers to the following practical questions: why change the maximal intercuspation (mICP) of a pa-tient? Where should a new mICP be constructed? When should invasive treatment be used?

Keywords Malocclusion · Dentistry · Conferences and proceedings · Temporomandibular joint · Prosthodontic

The following article attempts to summarize the impor-tant elements that were highlighted during the last congress of the International Academy of Advanced Interdisciplinary Dentistry (http://www.iaaidentistry.com) in association with the “Associazione Italia Gna-tologia”-. A total of 200 colleagues from 20 countries participated in the meeting held from 30 November to 2 December 2012 at the faculty of Dentistry Bernhard Got-tlieb Universitätszahnklinik, Vienna Austria. Talks were held by R. Slavicek (Austria), J.D. Orthlieb (France), S. Naretto (Italy), P. Carpentier (France), E. Úry (Hungary), G. Slavicek (Germany), E. Roshchin (Russia), Xiaohui-Rausch-Fan (Austria), S. Kulmer (Austria), Xiao-Jiang

Yang (China), A. Landry (Canada), M. Greven (Ger-many), P. Simeone (Italy), N. Bassetti (Italy), G. Reich-ardt (Germany), S. Cid (Portugal), R. Masnata (Italy), F. Ravasini, N. Gondoni (Italy), E. Tanteri (Italy), G. Dumi-nil (France), A. Knaus (Austria), H. Yoshimi (Japan) and S. Sato (Japan).

To think always means making a selection. To think about the mandibular therapeutic position means that there is the possibility of changing the situation of maxi-mal intercuspation (mICP). The objectives of the meeting were to propose answers to the following practical ques-tions: why change the mICP of a patient? Where should a new mICP be constructed? When should invasive treat-ment be used? The literature review presented during the meeting showed a large lack of scientific evidence so the contents of the following text should only be considered as proposals.

Why think about a new situation for the mICP?

• Isittoobtainanoptimizationofcondylo-disco-fossarelationship?

• Isittofacilitateprosthodontictreatmentbyprotrudedanterior repositioning, providing a better anterior oc-clusal relationship and more posterior space?

• IsitawaytoeasilyobtainaclassIduringorthodontictreatment?

Because it is more complicated, strong reasons are needed to treat a patient “out of his mICP” or sometimes “out of the centric relation”. It is probably possible to keep in memory simple principles, indicating to change the situation of the mICP:

• Temporomandibular joint (TMJ): to improve the ca-pacity to absorb mechanical stress (probably by pro-viding stability)

J. Stomat. Occ. Med. (2013) 6:115–119DOI 10.1007/s12548-013-0090-y

Interdisciplinary approach to the mandibular therapeutic position in oral rehabilitationElodie Ehrmann · Markus Greven · Jean-Philippe Ré · Jean-Daniel Orthlieb

J.-D. Orthlieb ()Faculté d’Odontologie, Aix-Marseille Université, 27, boulevard Jean Moulin, 13355 Marseille, Cedex 5, Francee-mail: jean-daniel.orthlieb@univ-amu.fr

E. EhrmannUniversité de Nice Sophia-Antipolis, Nice, France

M. GrevenKanagawa Dental College, Bohn, France

J.-P. RéAix-Marseille Université, Marseille, France

Received: 29 April 2013 / Accepted: 12 June 2013 / Published online: 29 October 2013© Springer-Verlag Wien 2013

116 Interdisciplinary approach to the mandibular therapeutic position in oral rehabilitation

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• Prosthesis:toincreasethecoronalposteriorspace• Occlusion:tooptimizetheanteriorocclusalrelations

and to obtain better posterior occlusal support and stability.

Where is the best situation for the mandibular therapeutic position?

In the case of an unstable TMJ related to a muscular dis-order, the muscular dysfunction must be treated before deciding on the condylar position.

If it is decided to change the condylar position the objectives could probably be to push the mandible slightly forward (sagittal plane) and to look for a more median condylar position (coronal plane).

The quantity of the anterior repositioning is depen-dant on:

• condylo-discalrelations• anteriorocclusalrelations:overjetvalue• posteriorocclusalrelations:one-oneoronetooth-two

teeth occlusions.

A new mICP in a protuded mandibular position more than 2  mm away from the articular reference position (centric relation) could cause a condylar transversal instability.

When to decide to change the mandibular position of maximal intercuspation?

Before answering this question it is necessary to specify what is meantby invasive treatment?

“Overtreatment” is a more pertinent term than “inva-sive treatment”. The most common conclusions in the literature on temporomandibular disorders (TMD) sug-gest that invasive treatment is contraindicated because this is considered to be overtreatment. There is prob-ably some confusion between invasive treatment and overtreatment.

• Invasive treatment changes some anatomical struc-tures in an irreversible way.

• Overtreatment isunnecessary treatment. If theover-treatment presents an invasive aspect, from an ana-tomical or psychological point of view it is a malprac-tice endangering the patient.

Some detailed literature reviews emphasize that if the oral condition generates a handicap for mastication this dental condition can impact the health and the longevity of the patient.

Even if the evidence is weak correction of dental defi-ciencies remains indicated in its classical forms (restor-ative dentistry, prosthetics, orthodontics). The goal of

treatment is a structural optimization (rather than ideal-ization) in a low cost individualized way.

In the presence of TMD and altered teeth conven-tional dental treatment is indicated. This treatment is invasive but justified by the dental status so there is no overtreatment.

This dental treatment is necessarily occlusal treatment which helps to optimize functions and behavior of the masticatory organ (e.g. correction of unilateral mastica-tion). This treatment does not constitute a therapeutic excess cost.

If numerous teeth have to be replaced the occlusion can be adjustable; however, a risk would be to convince the patient that dental treatment is indicated only to cor-rect bruxism, chronic myalgia or a simple click. In the patient’s mind it is dangerous to reduce the TMD treat-ment to the occlusal approach.

The notion of occlusal overtreatment concerns sub-jects with healthy dental arches. With the current level of evidence in healthy dentition the general rule of TMD treatment is intangible: no extensive occlusal treatment.

Where are the limits of overtreatment? A very poor dental status of a patient is an opening way towards an extensive occlusal treatment and in this case it is not an overtreatment. Therefore it is permitted to adjust the mandibular position to optimize occlusal functions, to improve stability of anatomical structures and to facili-tate numerous functions of the masticatory organ.

In patients with a perfectly healthy dentition the non-invasive approach, such as physiotherapy and behavioral reconditioning, will be the therapeutic approach and avoiding overtreatment.

For the practitioner the real difficulty is to consider where are the limits between eufunction (adaptation) and pathofunction are (structural instability and/or functional disability). Doubts by the practitioner should lead to a prudent attitude:

• To take time to analyze the clinical evolutionwith anoninvasive approach,

• To analyze the potential of occlusal modifications(without excess cost) to induce a therapeutic gain.

Reference position: decision-making algorithm

Before deciding which approach to use the current situ-ation must be assessed. This is the diagnostic phase. To establish a diagnosis a reference mandibular position is needed which is characterized by two criteria:

• non-pathogenic,whichmeansamandibleinitsphys-iological position.

• reproducibility.

Only two mandibular positions can meet these criteria (Fig. 1). When the mandible is:

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Interdisciplinary approach to the mandibular therapeutic position in oral rehabilitation 117

• Inmaximalintercuspation(mICP)itisintheocclusalreference position.

• In centric relation it is in the articular referenceposition.

The best choice, because it is the simplest one, will be to conserve the mICP, if the residual mICP is stable enough (residual means after crown preparations) and not trans-versally deflected. In this case, the mandibular reference position will be the occlusal reference position. Other-wise, a new mICP will be built in a centric relation, the articular reference position. Sometimes, the TMJ must be stabilized before by a musculoarticular recondition-ing phase.

Therapeutic position: decision-making algorithm

Once the reference position is selected, the choice of the therapeutic position can be made.

• Ifthereferencepositionistheocclusalreferenceposi-tion, the therapeutic position will necessarily be the initial mICP of the patient often reinforced by an orth-odontic or prosthodontic treatment.

• Ifthereferencepositionisthearticularreferenceposi-tion a new mICP has to be stabilized in the therapeu-tic position. There are two possibilities for the sagittal dimension:

− condyles in centric relation or− condyles in protruded position (anteposition).

In both cases, then and only then the vertical dimension must be chosen by rotation around the bicondylar hinge axis.

Because, unlike mathematics, there are often uncer-tainties in biology, it can be decided to conserve the initial mICP of the patient despite a lack of stability or a deflected position (deflected mICP means mICP devi-ated from occlusion in centric relation).

The decision criterion will be the ratio between the functional benefits and dental costs (orthodontic or prosthodontic), induced by the occlusal equilibration in the therapeutic position initially planned. In this case, the term used for the therapeutic position, is habitual mICP to underline its imperfect character (Fig. 2).

Occlusal splint and therapeutic position

The use of a splint phase during the treatment was fre-quently proposed by the presentations at the meeting before making modifications to the teeth. The objec-tives are either to facilitate or induce a musculoarticu-lar reconditioning or to test a new mandibular position changed in the sagittal or vertical direction.

A consensus seems to be in favor of a short duration of the splint phase, generally 2 or 3 months, only during sleeping time or all day in some cases.

If diagnosis protocols and reconstruction protocols are widely shared some questions about treatment remained controversial especially around the splint phase.

• Splintadjustments:eitherfrequentadjustmentsofthesplint are realized to adapt the therapeutic position or no modification to obtain musculoarticular adapta-tion to the position induced by the splint.

• Doesthesplintrepresentarealfunctionaltestforthetherapeutic position? The occlusal morphology, the thickness, the lack of proprioception, the modification of the tongue, lip functions and breathing can prob-ably influence the reactions. It is just a first approach,

Fig. 1 Decision-making algorithm: mandibular refer-ence position

118 Interdisciplinary approach to the mandibular therapeutic position in oral rehabilitation

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Fig. 3 Wax impression of the therapeutic position directly on the splint

Fig. 4 Clinical case ex-ample: initial situation dur-ing splint phase and final situation after orthodontic treatment

Fig. 2 Decision-making algorithm: mandibular therapeutic position

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Interdisciplinary approach to the mandibular therapeutic position in oral rehabilitation 119

which must be consolidated during the temporary prosthodontic phase.

• Afterthesplintphase,howshouldtheobtainedman-dibular position be transferred?

• Clearerprotocolsaboutthesepointsneedtobepro-posed if the therapeutic position concept is to remain consistent (Figs. 3 and 4).

Conflict of interest The authors declare that there are no actual or potential conflicts of interest in relation to this article.